Generally, an angle adjustable lamp has a support arm and a rotating arm. The support arm is assembled to a seat which can be seated upon a table surfaces or a platform so as to form as a stand lamp. The support arm can be directly to a wall to form as a suspending lamp. The support arm may be assembled with a lamp head which has a lamp and a lampshade. Moreover, the support arm is pivoted to the rotating arm so that the rotating arm is rotatable with respect to the support arm so as to control the angle of the lamp head. It should be noted that for retaining the rotating arm to a predetermined angle, as illustrated in FIG. 7, a prior art lamp has a rubber pad 3 installed between the support arm 1 and the rotating arm 2. A stud 4 serves to lock it so that the rubber pad 3 has the effect of slide stop to prevent that after adjustment of the angle, the rotating arm 2 will loose.
However although the rubber pad 2 has the effect of slide stop, but since the structural design will cause another end of the rotating arm 2 will suffer from a gravitation force so as to convert into a twisting torque to be applied to rubber pad 3 so that the pad 3 must suffer from the twisting torque. The rubber pad 3 is made of rubber. The rubber is easy to weaken as it is used for a longer time and thus deforms. Therefore, after the rubber pad 3 is used for a long time, the slide stop effect is reduced. The lamp cannot be steadily supported and fixed so as to shift and swing. As a result, the lamp cannot be steadily retained to an original position with a desired illumination.